This invention relates to a process for the preparation of linear aldehydes by hydroformylation of C2 to C20 monoethylenically unsaturated organic compounds in the presence of a Group VIII transition metal and selected multidentate phosphite ligands. The invention also relates to the selected multidentate phosphite ligands themselves, as well as hyroformylation catalysts made therefrom.
Phosphorus-based ligands are ubiquitous in catalysis and are used for a number of commercially important chemical transformations. Phosphorus-based ligands commonly used in catalysis include phosphines and phosphites. These ligands include monophosphine and monophosphite ligands, which are compounds that contain a single phosphorus atom that serves as a donor to a transition metal, and bisphosphine, bisphosphite, and bis(phosphorus) ligands, which contain two phosphorus donor atoms and normally form cyclic chelate structures with transition metals.
An industrially important catalytic reaction using phosphorus-based ligands is olefin hydroformylation. Phosphite ligands are particularly good ligands for these reactions. For example, U.S. Pat. No. 5,235,113 describes a hydroformylation process in which an organic bidentate ligand containing two phosphorus atoms linked with an organic dihydroxyl bridging group is used in a homogeneous hydroformylation catalyst system also comprising rhodium. This patent describes a process for preparing aldehydes by hydroformylation of ethylenically unsaturated organic compounds, for example 1-octene or dimerized butadiene, using the above catalyst system. The use of phosphite ligands with rhodium has been disclosed in the hydroformylation of functionalized ethylenically unsaturated compounds. See for example Cuny et al., J. Am. Chem. Soc., 1993, 115, 2066; U.S. Pat. Nos. 4,769,498, 4,668,651, 4,885,401, 5,113,022, 5,059,710, 5,235,113, 5,264,616, and 4,885,401; and published international applications WO9303839, and WO9518089.
Hydroformylation processes involving organic bidentate ligands containing an aromatic dihydroxyl bridging group and terminal aryl groups bearing heteroatom substituents are described in German Patent Application DE 19717359 A1.
Hydroformylation processes involving organic bidentate ligands containing two trivalent phosphorus atoms, in which the two phosphorous atoms are linked with a 2,2xe2x80x2-dihydroxyl-1,1xe2x80x2-binaphthalene bridging group, are described in U.S. Pat. No. 5,874,641 and the prior art referenced therein. U.S. Pat. No. 5,874,641 describes ligands containing substituents such as esters or ketones on the 3,3xe2x80x2-positions of the 2,2xe2x80x2-dihydroxyl-1,1xe2x80x2-binaphthalene bridging group. Such ligands provide reasonably good selectivity in the hydroformylation of internal olefins to terminal aldehydes.
Although some of these prior art systems involve commercially viable catalysts, there remains a need for even more effective catalyts to achieve even greater commercial potential. An object of this invention is to provide such improved catalysts for hydroformylation.
In one aspect, the present invention is a process for converting a C2 to C20 acyclic monoethylenically unsaturated compound to its corresponding terminal aldehyde, comprising reacting the compound with CO and H2 in the presence of a Group VIII transition metal and at least one multidentate phosphite ligand of the following formulae I, II or III: 
wherein:
each R1 independently is C1 to C12 alkyl, C6 to C20 aryl, F, Cl, xe2x80x94CO2R4, xe2x80x94OR4, or xe2x80x94R3Z, provided that at least one R1 is xe2x80x94R3Z;
each R2 independently is H, F, Cl, C1 to C12 alkyl, C6 to C20 aryl, xe2x80x94OR4, xe2x80x94CO2R4, xe2x80x94C(O)R4, xe2x80x94CHO, xe2x80x94CN, or xe2x80x94CF3;
each R3 independently is C1 to C10 alkylene;
each R4 independently is C1 to C12 alkyl or C6 to C20 aryl;
each Z is xe2x80x94CO2R4, xe2x80x94CHO, xe2x80x94C(O)R4, xe2x80x94C(O)SR4, xe2x80x94SR4, xe2x80x94C(O)NR5R6, xe2x80x94OC(O)R4, xe2x80x94OC(O)OR4, xe2x80x94Nxe2x95x90CR5R6, xe2x80x94C(R5)xe2x95x90NR6, xe2x80x94C(R5)xe2x95x90Nxe2x80x94Oxe2x80x94R6, xe2x80x94P(O) (OR4) (OR4), xe2x80x94S(O)2R4, xe2x80x94S(O)R4, xe2x80x94C(O)OC(O)R4, xe2x80x94NR4CO2R4, xe2x80x94NR4C(O)NR5R6, or xe2x80x94CN;
each R4 independently is C1 to C12 alkyl or C6 to C20 aryl;
each R5 independently is H, C1 to C12 alkyl, or C6 to C20 aryl;
each R6 independently is H, C1 to C12 alkyl, or C6 to C20 aryl;
Q is a divalent bridging group of the formula: 
xe2x80x83wherein:
each R7 independently is H, F, Cl, C1 to C12 alkyl, C6 to C20 aryl, xe2x80x94OR4, xe2x80x94CO2R4, xe2x80x94C(O)R4, xe2x80x94C(R5)xe2x95x90Nxe2x80x94Oxe2x80x94R6, xe2x80x94CHO, xe2x80x94CN, xe2x80x94CF3, xe2x80x94C(R5)xe2x95x90NR6, xe2x80x94NR5R6 or xe2x80x94R3Z; and
each R8 is H, F, Cl, C1 to C12 alkyl, C6 to C20 aryl, xe2x80x94OR4, xe2x80x94CO2R4, xe2x80x94C(O)R4, xe2x80x94CN, or xe2x80x94CF3.
The term xe2x80x9carylxe2x80x9d is meant to denote an organic radical which is derived from an aromatic hydrocarbon by removal of one atom. Suitable aryl radicals are, for example, phenyl, benzyl, naphthyl, binaphthyl, and anthracenyl. The terms xe2x80x9calkylxe2x80x9d and xe2x80x9calkylenexe2x80x9d are meant to denote both straight and branched groups.
In another aspect, this invention provides for the above multidentate phosphite ligands and catalyst compositions made therefrom.
Any of the above ligands optionally may be attached to a soluble or insoluble inert support. An example of an insoluble inert support is Merrifield""s resin (a functionalized polystyrene resin commercially available from Aldrich Chemical Company).
This invention provides a process for the preparation of terminal aldehydes with high catalyst performance (selectivity and/or activity). The advantages of the present process are particularly pronounced when the reactant is an internally monoethylenically unsaturated compound. Preparing terminal aldehydes starting from internally monoethylenically unsaturated compounds using previously known hydroformylation processes generally results in moderate selectivity to terminal aldehydes, some hydrogenation of the double bond and/or lower catalytic activity. An additional advantage of the process according to the present invention is that the linearity [terminal aldehydes/(terminal+branched aldehydes)] is high, facilitating the isolation of the desired terminal aldehyde from a mixture of terminal and branched aldehydes.
The catalyst compositions useful in the processes of the invention comprise selected multidentate phosphite ligands and a Group VIII transition metal, which is provided in the form of a chemical compound.
The multidentate phosphite ligand is of the formulae I, II or III: 
wherein:
each R1 independently is C1 to C12 alkyl, C6 to C20 aryl, F, Cl, xe2x80x94CO2R4, xe2x80x94OR4, or xe2x80x94OR3Z, provided that at least one R1 is xe2x80x94R3Z;
each R2 independently is H, F, Cl, C1 to C12 alkyl, C6 to C20 aryl, xe2x80x94OR4, xe2x80x94CO2R4, xe2x80x94C(O)R4, xe2x80x94CHO, xe2x80x94CN, or xe2x80x94CF3;
each R3 independently is C1 to C10 alkylene;
each R4 independently is C1 to C12 alkyl or C6 to C20 aryl;
each Z is xe2x80x94CO2R4, xe2x80x94CHO, xe2x80x94C(O)R4, xe2x80x94C(O)SR4, xe2x80x94SR4, xe2x80x94C(O)NR5R6, xe2x80x94OC(O)R4, xe2x80x94OC(O)OR4, xe2x80x94Nxe2x95x90CR5R6, xe2x80x94C(R5)xe2x95x90NR6, xe2x80x94C(R5)xe2x95x90Nxe2x80x94Oxe2x80x94R6, xe2x80x94P(O) (OR4) (OR4) xe2x80x94S(O)2R4, xe2x80x94S(O)R4, xe2x80x94C(O)OC(O)R4, xe2x80x94NR4CO2R4, xe2x80x94NR4C(O)NR5R6, or or xe2x80x94CN;
each R4 independently is C1 to C12 alkyl or C6 to C20 aryl;
each R5 independently is H, C1 to C12 alkyl, or C6 to C20 aryl;
each R6 independently is H, C1 to C12 alkyl, or C6 to C20 aryl;
Q is a divalent bridging group of the formula: 
xe2x80x83wherein:
each R7 independently is H, F, Cl, C1 to C12 alkyl, C6 to C20 aryl, xe2x80x94OR4, xe2x80x94CO2R4, xe2x80x94C(O)R4, xe2x80x94(R5)xe2x95x90Nxe2x80x94Oxe2x80x94R6, xe2x80x94CHO, xe2x80x94CN, xe2x80x94CF3, xe2x80x94C(R5)xe2x95x90NR6, xe2x80x94NR5R6 or xe2x80x94R3Z; and
each R8 is H, F, Cl, C1 to C12 alkyl, C6 to C20 aryl, OR4, xe2x80x94CO2R4, xe2x80x94C(O)R4, xe2x80x94CN, or xe2x80x94CF3.
Preferred multidentate phosphite ligands are of the following formula I: 
wherein:
each R1 independently is xe2x80x94R3Z;
each R2 independently is H, F, Cl, C1 to C12 alkyl, C6 to C20 aryl, xe2x80x94OR4, xe2x80x94CO2R4, xe2x80x94C(O)R4, xe2x80x94CHO, xe2x80x94CN, or xe2x80x94CF3;
each R3 independently is C1 to C4 alkylene;
each Z independently is xe2x80x94CO2R4, xe2x80x94CHO, xe2x80x94C(O)R4, xe2x80x94C(O)NR5R6, xe2x80x94OC(O)R4, xe2x80x94OC(O)OR4, xe2x80x94Nxe2x95x90CR5R6, or xe2x80x94C(R5)xe2x95x90NR6;
Q is a divalent bridging group of the formula: 
xe2x80x83wherein:
each R7 independently is xe2x80x94CO2R4, xe2x80x94C(O)R4, xe2x80x94C(R5)xe2x95x90Nxe2x80x94Oxe2x80x94R6, xe2x80x94CHO, xe2x80x94CN, or xe2x80x94C(R5)xe2x95x90N(R6); and
each R8 independently is H, F, Cl, C1 to C12 alkyl, C6 to C20 aryl, xe2x80x94OR4, xe2x80x94CO2R4, xe2x80x94C(O)R4, xe2x80x94CN, or xe2x80x94CF3.
The multidentate phosphite ligands of the present invention can be prepared by using a process in which a phosphorochloridite is reacted with a divalent bridging group. The phosphorochloridite can be prepared by treating at a temperature between about xe2x88x9240xc2x0 C. and 10xc2x0 C. one molar equivalent of PCl3 with about two molar equivalents of substituted phenol in the absence of an organic base. The resulting solution is then treated with at least two equivalents of an organic base to produce a phosphorochloridite. When the substituted phenols are replaced with substituted biphenol or substituted alkylidenebisphenol, the phosphorochloridite is similarly prepared from initially mixing one molar equivalent of PCl3 with about one molar equivalent of substituted biphenol or substituted alkylidenebisphenol between about xe2x88x9240xc2x0 C. and 10xc2x0 C. in the absence of an organic base. The resulting solution is then treated with at least two equivalents of an organic base to produce a phosphorochloridite.
When preparing the phosphorochloridite in the above manner, it is important to maintain temperature in the xe2x88x9240xc2x0 C. and 10xc2x0 C. range during the base addition. The addition of base results in the formation of an insoluble salt formed by neutralizing HCl, and the reaction mixture can become a thick slurry. Such a slurry can create problems in achieving good mixing of base which is important in avoiding temperature gradients in the reaction mixture which can decrease yield of the desired product. It is important, therefore, that the reaction be conducted with vigorous stirring or other agitation to allow effective removal of heat from the reaction mixture. Cooling to the required temperature range can be accomplished by well-known techniques in the art.
At a temperature range between xe2x88x9240xc2x0 C. and 70xc2x0 C., the phosphorochloridite is reacted with about a half molar equivalent of the divalent bridging group. If less than three equivalents of the organic base were utilized in preparing the phosphorochloridite, additional organic base is added to bring the total equivalents of organic base utilized in the process to at least three.
The base used in preparing the multidentate phosphite ligands should be anhydrous and soluble in the reaction medium. Suitable bases are organic amines. Especially preferred are trialkylamines. The most preferred bases are selected from the group consisting of tributylamine, benzyldimethylamine, triethylamine, and diisopropylmethylamine.
The phosphorochloridites can be prepared by a variety of other methods known in the art. One method involves treating phenols with PCl3, such as described in, Polymer 1992, 33, 161; Inorganic Syntheses, 1966, 8, 68; U.S. Pat. No. 5,210,260; and Z. Anorg. Allg. Chem., 1986, 535, 221.
When the phosphorochloridite cannot be prepared in good yield from PCl3, the preferred method involves the treatment of N,N-dialkyl diarylphosphoramidite derivatives with HCl. The N,N-dialkyl diarylphosphoramidite is of the form (R9)2NP(aryloxy)2 where R9 is a C1 to C4 alkyl group, and can be obtained by reacting phenol or substituted phenol with (R9)2NPCl2 by methods known in the art, such as described in WO9622968, U.S. Pat. Nos. 5,710,306, and 5,821,378. The N,N-dialkyl diarylphosphoramidites may be prepared, for example, as described in Tet. Lett., 1993, 34,6451; Synthesis, 1988, 2, 142-144, and Aust. J. Chem., 1991, 44, 233.
The multidentate phosphite ligand does not have to be pure to be used in the process of the present invention; it can contain some monodentate phosphites as impurities.
Multidentate phosphite ligands may be supported on soluble or insoluble inert supports. Polymer-supported multidentate phosphorus ligands may be prepared by a variety of methods known in the art. See WO9303839, U.S. Pat. Nos. 4,769,498 and 4,668,651, and WO9906146. In general, the preparation involves the reaction of a phosphorus halide, typically but not limited to, chloride, with a diol to form Pxe2x80x94O bonds. A representative example is shown below. 
xe2x80x9cPolxe2x80x9d denotes the soluble or insoluble inert support. R1 and R7 are as defined above.
A specific example of an insoluble inert support is Merrifield""s resin (a functionalized polystyrene resin available from Aldrich Chemical Company). The above diol may be prepared by first partial esterification of 2,2xe2x80x2-dihydroxyl-1,1xe2x80x2-binaphthalene-3,3xe2x80x2-dicarboxylic acid with Merrifield""s resin, followed by esterification of the resulting ester/acid diol intermediate. The esterification conditions are well known to those skilled in the art of organic synthesis.
The invention also provides for certain multidentate phosphite ligands and catalyst compositions made therefrom. In particular, these include the ligands of Formula I, II or III and the combination of a ligand of Formula I, II or III with a Group VIII transition metal compound. Preferred Group VIII transition metals are rhodium, cobalt, iridium, palladium and platinum, the most preferred being rhodium. The Group VIII metal is provided in the form of a compound, such as a hydride, halide, organic acid salt, ketonate, inorganic acid salt, oxide, carbonyl compound or amine compound. Preferred Group VIII metal compounds are Ir4(CO)12, IrSO4, RhCl3, Rh(NO3)3, Rh(OAc)3, Rh2O3, Rh(acac)(CO)2, [Rh(OAc)(COD)]2, Rh4(CO)12, Rh6(CO)16, RhH(CO)(Ph3P)3, [Rh(OAc)(CO)2]2, and [RhCl(COD)]2 (wherein xe2x80x9cacacxe2x80x9d is an acetylacetonate group; xe2x80x9cOAcxe2x80x9d is an acetyl group; xe2x80x9cCODxe2x80x9d is 1,5-cyclooctadiene; and xe2x80x9cPhxe2x80x9d is a phenyl group). However, it should be noted that the Group VIII metal compounds are not necessarily limited to the above listed compounds. The rhodium compounds, suitable for hydroformylation, can be prepared or generated according to techniques well known in the art, as described, for example, in WO 95 30680, U.S. Pat. No. 3,907,847, and J. Amer. Chem. Soc., 115, 2066, 1993. Rhodium compounds that contain ligands which can be displaced by the present multidentate phosphite ligands are a preferred source of rhodium. Examples of such preferred rhodium compounds are Rh(CO)2 (acac), Rh(CO)2(C4H9COCHCO-t-C4H9), Rh2O3, Rh4(CO)12, Rh6(CO)16, Rh(O2CCH3)2, and Rh(2-ethylhexanoate).
The reactant of the present process is a monoethylenically unsaturated organic compound having at least one xe2x80x9cCxe2x95x90Cxe2x80x9d bond in the molecule and preferably 2 to 20 carbon atoms. Examples of suitable ethylenically unsaturated organic compounds are linear terminal olefinic hydrocarbons, for example, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and 1-dodecene; branched terminal olefinic hydrocarbons, for example, isobutene and 2-methyl-1-butene; linear internal olefinic hydrocarbons, for example, cis- and trans-2-butene, cis- and trans-2-hexene, cis- and trans-2-octene, cis- and trans-3-octene; branched internal olefinic hydrocarbons, for example, 2,3-dimethyl-2-butene, 2-methyl-2-butene and 2-methyl-2-pentene; terminal olefinic hydrocarbons; internal olefinic hydrocarbon mixtures; for example, octenes, prepared by dimerization of butenes.
Examples of suitable olefinic compounds include those substituted with an unsaturated hydrocarbon group, including olefinic compounds containing an aromatic substituent such as styrene, alpha-methylstyrene and allylbenzene.
The ethylenically unsaturated organic compound can be substituted with one or more functional groups containing a heteroatom, such as oxygen, sulfur, nitrogen or phosphorus. Examples of these heteroatom-substituted ethylenically unsaturated organic compounds include vinyl methyl ether, methyl oleate, oleyl alcohol, 3-pentenenitrile, 4-pentenenitrile, 3-pentenoic acid, 4-pentenoic acid, methyl 3-pentenoate, 3-pentenal, allyl alcohol, 7-octen-1-al, acrylonitrile, acrylic acid esters, methyl acrylate, methacrylic acid esters, methyl methacrylate, and acrolein.
The invention is especially directed to hydroformylation processes in which a linear aldehyde compound is prepared starting from internal monoethylenically unsaturated organic compounds with 2 to 20 carbon atoms.
Preferred monoethylenically unsaturated compounds that are useful in the process of this invention are shown in Formulas IV and VI, and the corresponding terminal aldehyde compounds produced are illustrated by Formulas V and VII, respectively. 
wherein
R10 is H, xe2x80x94CN, xe2x80x94CO2R5, xe2x80x94C(O)NR5R6, xe2x80x94CHO, xe2x80x94OR4, or OH;
y is an integer from 0 to 12;
x is an integer from 0 to 12;
R4, R5 and R6 are as defined above.
Particularly preferred internal monoethylenically unsaturated organic compounds are 3-pentenenitrile, 3-pentenoic acid, and alkyl 3-pentenoate, such as methyl 3-pentenoate. The linear aldehyde compound prepared by the present process starting with one of these compounds can be used advantageously in the preparation of xcex5-caprolactam, hexamethylenediamine, 6-aminocaproic acid, 6-aminocapronitrile or adipic acid, which are precursors for Nylon-6 and/or Nylon-6,6.
The 3-pentenenitrile may be present in mixtures containing 4-pentenenitrile. Similarly, when alkyl 3-pentenoate or 3-pentenoic acid is the reactant used in the present process, mixtures containing alkyl 4-pentenoate or 4-pentenoic acid, respectively, may be present. Because the 4-isomers of these compounds react in a similar fashion as their corresponding 3-isomers to the desired linear aldehyde, a mixture of isomers can be used directly in the present process. Hydroformylation of these 3- and 4-isomer can be carried out in the presence of 2-isomers. Impurities can be present as long as they do not interfere with the reaction.
The hydroformylation process according to the invention can be performed as described below.
The reaction conditions of the hydroformylation process are, in general, the same as those used in a conventional process, described for example in U.S. Pat. No. 4,769,498, and will be dependent on the particular starting monoethylenically unsaturated organic compound. For example, the temperature can be from ambient temperature to 200xc2x0 C., preferably from about 50 to 150xc2x0 C., and more preferably from 85xc2x0 to 110xc2x0 C. The pressure may vary from normal pressure to 5 MPa, preferably from 0.1 to 2 MPa. The pressure is, as a rule, equal to the combined hydrogen and carbon monoxide partial pressures. However, extra inert gases may also be present; the pressure may vary from normal pressure to 15 MPa when inert gases are present. The molar ratio of hydrogen to carbon monoxide is generally between 10:1 and 1:10, and preferably between 6:1 and 1:2.
The amount of transition metal compound is selected so that favorable results can be obtained with respect to catalyst activity and process economy. In general, the concentration of transition metal in the reaction medium is between 10 and 10,000 ppm and more preferably between 50 and 1000 ppm, calculated as free metal.
The molar ratio of phosphorus ligand to transition metal is selected so that favorable results can be obtained with respect to catalyst activity and desired aldehdye selectivity. This ratio generally is from about 0.5 to 100 and preferably from 1 to 20 (moles phosphorus per mole metal).
The solvent may be the mixture of reactants of the hydroformylation reaction itself, such as the starting unsaturated compound, the aldehyde product and/or by-products. Other suitable solvents include saturated hydrocarbons (for example, kerosene, mineral oil, or cyclohexane), ethers (for example, diphenyl ether or tetrahydrofuran), ketones (for example, acetone, cyclohexanone), nitrites (for example, acetonitrile, adiponitrile or benzonitrile), aromatics (for example, toluene, benzene, or xylene), esters (for example, methyl valerate, caprolactone), Texanol(copyright) (Union Carbide), or dimethylformamide.